Heat Acclimation and HSP-72 Expression in Exercising Humans

Abstract

The purpose of this research was to determine the effect of a 7-day heat acclimation protocol on HSP-72 expression in human skeletal muscle, and to examine the relationships between molecular and physiological markers of heat acclimation. Ten recreationally active male subjects (age = 23.3 ± 2.81 yrs, V·O_2peak = 3.85 ± 0.11 L · min^-1) completed a 7-day heat acclimation protocol consisting of cycling at 75 % of V·O_2peak in a hot environment (39.5 °C, 27 % RH). Muscle biopsies were obtained on days 1 (HTT1) and 7 (HTT2) prior to, 6 h post, and 24 h postexercise to measure HSP-72 protein via SDS-PAGE and silver staining. Core rectal temperatures (T_C), intramuscular temperatures (T_IM), skin temperatures (T_SK), heart rate (HR), oxygen uptake (V·O₂), sweat rate (SR), and plasma cortisol were measured. TC, HR, and plasma cortisol were significantly lower in HTT2 than HTT1 (p ≤ 0.05). No significant differences were seen for V·O₂, TIM, TSK, or SR when comparing HTT2 with HTT1 (p ≤ 0.05). No significant time or day × time interactions were detected for HSP-72 expression (24.48 ± 2.55 vs. 25.04 ± 1.43 ng/µg protein for HTT1 and HTT2, respectively, p ≤ 0.05). Evidence of heat acclimation was seen at the physiological level; however, no evidence of enhanced thermotolerance at the cellular level was indicated by HSP-72 expression.

HSP‐72 - core temperature - intramuscular temperature - environmental stress

References

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